drivers/cpufreq/cpufreq_userspace.c

   1
   2 /*
   3  *  linux/drivers/cpufreq/cpufreq_userspace.c
   4  *
   5  *  Copyright (C)  2001 Russell King
   6  *            (C)  2002 - 2004 Dominik Brodowski <linux@brodo.de>
   7  *
   8  * This program is free software; you can redistribute it and/or modify
   9  * it under the terms of the GNU General Public License version 2 as
  10  * published by the Free Software Foundation.
  11  *
  12  */
  13
  14 #include <linux/kernel.h>
  15 #include <linux/module.h>
  16 #include <linux/smp.h>
  17 #include <linux/init.h>
  18 #include <linux/spinlock.h>
  19 #include <linux/interrupt.h>
  20 #include <linux/cpufreq.h>
  21 #include <linux/cpu.h>
  22 #include <linux/types.h>
  23 #include <linux/fs.h>
  24 #include <linux/sysfs.h>
  25 #include <linux/mutex.h>
  26
  27 #include <asm/uaccess.h>
  28
  29
  30 /**
  31  * A few values needed by the userspace governor
  32  */
  33 static unsigned int     cpu_max_freq[NR_CPUS];
  34 static unsigned int     cpu_min_freq[NR_CPUS];
  35 static unsigned int     cpu_cur_freq[NR_CPUS]; /* current CPU freq */
  36 static unsigned int     cpu_set_freq[NR_CPUS]; /* CPU freq desired by userspace */
  37 static unsigned int     cpu_is_managed[NR_CPUS];
  38
  39 static DEFINE_MUTEX     (userspace_mutex);
  40
  41 #define dprintk(msg...) cpufreq_debug_printk(CPUFREQ_DEBUG_GOVERNOR, "userspace", msg)
  42
  43 /* keep track of frequency transitions */
  44 static int
  45 userspace_cpufreq_notifier(struct notifier_block *nb, unsigned long val,
  46                        void *data)
  47 {
  48         struct cpufreq_freqs *freq = data;
  49
  50         dprintk("saving cpu_cur_freq of cpu %u to be %u kHz\n", freq->cpu, freq->new);
  51         cpu_cur_freq[freq->cpu] = freq->new;
  52
  53         return 0;
  54 }
  55
  56 static struct notifier_block userspace_cpufreq_notifier_block = {
  57         .notifier_call  = userspace_cpufreq_notifier
  58 };
  59
  60
  61 /**
  62  * cpufreq_set - set the CPU frequency
  63  * @freq: target frequency in kHz
  64  * @cpu: CPU for which the frequency is to be set
  65  *
  66  * Sets the CPU frequency to freq.
  67  */
  68 static int cpufreq_set(unsigned int freq, struct cpufreq_policy *policy)
  69 {
  70         int ret = -EINVAL;
  71
  72         dprintk("cpufreq_set for cpu %u, freq %u kHz\n", policy->cpu, freq);
  73
  74         lock_cpu_hotplug();
  75         mutex_lock(&userspace_mutex);
  76         if (!cpu_is_managed[policy->cpu])
  77                 goto err;
  78
  79         cpu_set_freq[policy->cpu] = freq;
  80
  81         if (freq < cpu_min_freq[policy->cpu])
  82                 freq = cpu_min_freq[policy->cpu];
  83         if (freq > cpu_max_freq[policy->cpu])
  84                 freq = cpu_max_freq[policy->cpu];
  85
  86         /*
  87          * We're safe from concurrent calls to ->target() here
  88          * as we hold the userspace_mutex lock. If we were calling
  89          * cpufreq_driver_target, a deadlock situation might occur:
  90          * A: cpufreq_set (lock userspace_mutex) -> cpufreq_driver_target(lock policy->lock)
  91          * B: cpufreq_set_policy(lock policy->lock) -> __cpufreq_governor -> cpufreq_governor_userspace (lock userspace_mutex)
  92          */
  93         ret = __cpufreq_driver_target(policy, freq, CPUFREQ_RELATION_L);
  94
  95  err:
  96         mutex_unlock(&userspace_mutex);
  97         unlock_cpu_hotplug();
  98         return ret;
  99 }
 100
 101
 102 /************************** sysfs interface ************************/
 103 static ssize_t show_speed (struct cpufreq_policy *policy, char *buf)
 104 {
 105         return sprintf (buf, "%u\n", cpu_cur_freq[policy->cpu]);
 106 }
 107
 108 static ssize_t
 109 store_speed (struct cpufreq_policy *policy, const char *buf, size_t count)
 110 {
 111         unsigned int freq = 0;
 112         unsigned int ret;
 113
 114         ret = sscanf (buf, "%u", &freq);
 115         if (ret != 1)
 116                 return -EINVAL;
 117
 118         cpufreq_set(freq, policy);
 119
 120         return count;
 121 }
 122
 123 static struct freq_attr freq_attr_scaling_setspeed =
 124 {
 125         .attr = { .name = "scaling_setspeed", .mode = 0644, .owner = THIS_MODULE },
 126         .show = show_speed,
 127         .store = store_speed,
 128 };
 129
 130 static int cpufreq_governor_userspace(struct cpufreq_policy *policy,
 131                                    unsigned int event)
 132 {
 133         unsigned int cpu = policy->cpu;
 134         switch (event) {
 135         case CPUFREQ_GOV_START:
 136                 if (!cpu_online(cpu))
 137                         return -EINVAL;
 138                 BUG_ON(!policy->cur);
 139                 mutex_lock(&userspace_mutex);
 140                 cpu_is_managed[cpu] = 1;
 141                 cpu_min_freq[cpu] = policy->min;
 142                 cpu_max_freq[cpu] = policy->max;
 143                 cpu_cur_freq[cpu] = policy->cur;
 144                 cpu_set_freq[cpu] = policy->cur;
 145                 sysfs_create_file (&policy->kobj, &freq_attr_scaling_setspeed.attr);
 146                 dprintk("managing cpu %u started (%u - %u kHz, currently %u kHz)\n", cpu, cpu_min_freq[cpu], cpu_max_freq[cpu], cpu_cur_freq[cpu]);
 147                 mutex_unlock(&userspace_mutex);
 148                 break;
 149         case CPUFREQ_GOV_STOP:
 150                 mutex_lock(&userspace_mutex);
 151                 cpu_is_managed[cpu] = 0;
 152                 cpu_min_freq[cpu] = 0;
 153                 cpu_max_freq[cpu] = 0;
 154                 cpu_set_freq[cpu] = 0;
 155                 sysfs_remove_file (&policy->kobj, &freq_attr_scaling_setspeed.attr);
 156                 dprintk("managing cpu %u stopped\n", cpu);
 157                 mutex_unlock(&userspace_mutex);
 158                 break;
 159         case CPUFREQ_GOV_LIMITS:
 160                 mutex_lock(&userspace_mutex);
 161                 dprintk("limit event for cpu %u: %u - %u kHz,"
 162                         "currently %u kHz, last set to %u kHz\n",
 163                         cpu, policy->min, policy->max,
 164                         cpu_cur_freq[cpu], cpu_set_freq[cpu]);
 165                 if (policy->max < cpu_set_freq[cpu]) {
 166                         __cpufreq_driver_target(policy, policy->max,
 167                                                 CPUFREQ_RELATION_H);
 168                 }
 169                 else if (policy->min > cpu_set_freq[cpu]) {
 170                         __cpufreq_driver_target(policy, policy->min,
 171                                                 CPUFREQ_RELATION_L);
 172                 }
 173                 else {
 174                         __cpufreq_driver_target(policy, cpu_set_freq[cpu],
 175                                                 CPUFREQ_RELATION_L);
 176                 }
 177                 cpu_min_freq[cpu] = policy->min;
 178                 cpu_max_freq[cpu] = policy->max;
 179                 cpu_cur_freq[cpu] = policy->cur;
 180                 mutex_unlock(&userspace_mutex);
 181                 break;
 182         }
 183         return 0;
 184 }
 185
 186
 187 struct cpufreq_governor cpufreq_gov_userspace = {
 188         .name           = "userspace",
 189         .governor       = cpufreq_governor_userspace,
 190         .owner          = THIS_MODULE,
 191 };
 192 EXPORT_SYMBOL(cpufreq_gov_userspace);
 193
 194 static int __init cpufreq_gov_userspace_init(void)
 195 {
 196         cpufreq_register_notifier(&userspace_cpufreq_notifier_block, CPUFREQ_TRANSITION_NOTIFIER);
 197         return cpufreq_register_governor(&cpufreq_gov_userspace);
 198 }
 199
 200
 201 static void __exit cpufreq_gov_userspace_exit(void)
 202 {
 203         cpufreq_unregister_governor(&cpufreq_gov_userspace);
 204         cpufreq_unregister_notifier(&userspace_cpufreq_notifier_block, CPUFREQ_TRANSITION_NOTIFIER);
 205 }
 206
 207
 208 MODULE_AUTHOR ("Dominik Brodowski <linux@brodo.de>, Russell King <rmk@arm.linux.org.uk>");
 209 MODULE_DESCRIPTION ("CPUfreq policy governor 'userspace'");
 210 MODULE_LICENSE ("GPL");
 211
 212 fs_initcall(cpufreq_gov_userspace_init);
 213 module_exit(cpufreq_gov_userspace_exit);